1. Field of the Invention.
The field of the invention is modifications to internal combustion engine carburetors to manually adjust the fuel rate flow through the main metering jets .
2. Description of the Related Art.
In the world of high performance internal combustion engines utilized primarily in racing cars and high speed boats, engine performance is dependent upon many different factors. One of the factors which effects engine performance at any one time is the environmental conditions, namely the air temperature, humidity, and altitude. In consideration of these environmental factors, the main metering jets on the engine carburetor through which the fuel is regulated to the engine becomes of utmost importance.
Presently, most high performance engines are adapted to use Holley brand high performance carburetors of the modular type, usually of 4-barrel configuration, where the carburetor has a main center section module containing four down draft venturi air throats into which the fuel is sprayed to be atomized, the fuel/air mixture then proceeding to the intake manifold and on to the individual cylinders through the intake valves. Attached on opposite sides of the carburetor main body module are the left and right metering block modules which, among other purposes, provide a passageway for the fuel moving into each of the throats of the carburetor 4-barrels. Adjacent each of the metering block modules are the float bowl modules which may be analogous to an open cup laying on its side. The float bowl module attaches to the metering block in a liquid-tight configuration, utilizing a gasket, and holds fuel interiorly at a fixed level generally determined by a float operated valve.
The fuel passageway in the fuel metering block communicates to the float bowl module at a point below the level of the fuel in the float bowl module and terminates into a larger diameter threaded hole into which the main metering jet is screwed. The main metering jet is thus totally below the fuel level in the float bowl module and has a longitudinal orifice therethrough which is of a fixed diameter, this orifice being the means by which fuel is metered from the float bowl module through the metering block and into the throat of one of the barrels of the carburetor main body module. If the carburetor is of the 4 "barrel" type, there will be four main metering jets, one for each barrel with two on each side of the carburetor protruding into the float bowl module.
The present state of the art requires that a racing enthusiast carry with him four sets of not less than six, nor usually more than twelve, individual standard stock main metering jets, each having a fuel metering orifice of a different diameter, each metering jet being the optimum jet for one set of particular environmental conditions. Currently, the Holley brand standard stock main metering jets Numbers 78 through 84 are the most common used by the inventor. The particular number of a jet does not necessarily correspond to the diameter of the orifice, but is merely a system of identifying different diameter jets.
Depending upon the various conditions under which the racer is to run his high performance engine, if a change of main metering jets is required, the operator must now firstly remove the fuel line to the float bowl module, remove the float bowl module from each side of the carburetor, spilling the gas in the module at that time upon the engine, and then unscrew each of the two main metering jets threaded into the two metering blocks. Then the operator must screw in the desired main metering jets and then reattach each of the float bowl modules to the metering blocks. The engine is then tested and if the operator selected the wrong size metering jet, he must select another jet and repeat the operation. Since a liquid-tight gasket fits between the edge of the float bowl module and the metering block module, the operator must be sure that the gasket is properly in place, and, that the gasket is not worn such that fuel might leak past it. The float bowl module is held to the metering block module by 2 to 4 elongated screws which surround the float bowl module.
Obviously the above operation takes some considerable time to accomplish and there's always the opportunity that anticipating certain weather conditions, the jets were changed some time prior to the race, however, the environmental conditions changed immediately prior to the race and the operator is left with insufficient time to make the race with the proper jets. Such would be the case at the occurrence of a sudden thunder storm which would add large amounts of humidity to the air. The inventor has experienced situations where he was unable to enter into a planned race because there was not sufficient time to change the main metering jets on the carburetor between the time that it was decided such a change was necessary and the start of the race.
Prior art devices regulating fuel flow in modular type carburetors are known, for example Johnson, in U.S. Pat. No. 3,807,707 details a device providing for adjustment of fuel moving in an inserted plate between the fuel reservoir and the carburetor main body. Such device requires a totally new manufactured part and the adjustment is made from the top of the carburetor which may require the prior removal of the carburetor air cleaner.
Accordingly, it is obvious that the need for a method and apparatus by which the effective orifice size of the main metering jets may be changed upon a minute's notice and accomplished within a minute or so without having to break down the carburetor modules and as such would be a great improvement in racing efficiency.